1. Field of the Invention:
This invention relates to water pump devices and more particularly to water pump devices which include double impellers for use in two independent water cooling systems for internal combustion engines.
2. Background of the Related Art:
In a conventional water pump device as shown in FIG. 2 and disclosed in, for example, Japanese Utility Model Laid Open No. 59-142493, a pump housing 20 has an intermediate plate 21 to thereby define independent first and second chambers 22 and 23. A pump shaft 24 which is rotatably supported in the housing 20 extends through the intermediate plate 21. A pair of pump impellers 25 and 26 are mounted on the shaft 24 and are positioned within the chambers 22 and 23, respectively. Disposed between the intermediate plate 21 and the shaft 24 is a seal member 27.
In the above prior art, two pump impellers 25 and 26 are formed independently so that the construction of the pump device becomes complex. Furthermore, since the seal member 27 is formed as contact type seal, the loss of pump torque increases due to the sliding resistance at the contact portion between the seal member 27 and the shaft 24. This results in a decrease in pump efficiency.